The Social Sciences Research Network is one of the largest and most active open access subject repositories:http://www.ssrn.com/

The Stanford Encyclopedia of Philosophy was an early innovator in the creation of a scholar-led open access encyclopedia and the development of the ongoing OA via creation of an endowment fund model (still promising, but as one might guess the financial crisis slowed this approach down a little):http://plato.stanford.edu/

The Public Knowledge Project, initiated by education researcher John Willinsky, created the Open Journal Systems used by about 15,000 journals around the world, about half of which are open access:http://pkp.sfu.ca/